The red, yellow and green dyes that give curries their familiar brightness are being used to potentially damaging levels, according to trading standards officers.

Restaurants say that bright is what we want

North Yorkshire officers have led the battle against the harmful agents by visiting 23 restaurants in the county.

They found 17 using more than the legal limit for colourings.

Gordon Gresty, of North Yorkshire Trading Standards, said: "In some instances they were four times above. We consider that to be quite serious."

Fines can reach £5,000

Fines of up to £5,000 can be imposed for misusing such dyes.

The Megna restaurant in Selby has become the first in the area to be fined. It was order to pay £200 plus £150 costs.

Colourings such as tartrazine can be especially harmful to asthma sufferers and those with skin allergies.

But the problem is not confined to restaurants.

Dr Tim Lobstein of the Food Commission said: "There are large numbers of colourings and additives that manufacturers love to use both for processed foods and for fast foods."